"You're 9 months old today," the Keeping Up With the Kardashians star said as she showed her youngest child with glasses and a grey mustache. "What an old man you are." The cutie, whose dad is Kanye West, smiled and giggled in delight.

The Selfish author then used the deer filter on her baby boy. "Are you the cutest little deer I ever saw?" she said, before posting a video of both of them with the same filter.

Kardashian, 35, often shares sweet videos with the couple's daughter, North, but the 3-year-old initially told her mom she was "scared" of Snapchat. She has warmed up to the social media app since then, and last week was spotted laughing as her mom face-swapped with her rapper spouse and superimposed West's face onto her body as she told her daughter to go to bed. Instead of freaking out at the sight of the scary hybrid, North rolled around on the bed laughing.

Since welcoming Saint in December 2015, Kardashian has mostly kept her baby out of the public eye.

"I wasn't posting about my son because I want him to go to the park like every normal human being," she explained back in August. "But some people thought I had a full fake baby because I wasn’t posting. … I'm protective of my life with my kids. You might see them on the show a bit, but not real stories."